Real-time monitoring of flavor-active compounds in beer using a portable FT-IR device

The aim of this study was to evaluate the feasibility of portable Fourier transform mid-infrared (FTIR) spectrometer coupled with pattern recognition modeling for the real–time monitoring of flavor-active compounds and multiple beer quality parameters. A total of 151 commercial beer samples spanning 35 styles were analyzed. Three targeted volatile organic compounds (VOCs), including isoamyl alcohol, furfural, and acetic acid were analyzed using gas chromatography with flame ionization detection (GC-FID). Beer stalling reactions were accelerated by exposing fresh degassed beer to ambient air for 12 h followed by a 60 °C heat incubation for 1 h to expand the concentration ranges of furfural reach beyond its sensory thresholds. Quality parameters (ethanol content, specific gravity, real extract, color, pH, iso-alpha acid content) were measured using standard laboratory reference methods from the American Society of Brewing Chemists. Partial least squares regression (PLSR) models were developed using FTIR spectral data and reference data for quantification purposes. All VOC models showed robust correlations between predicted and reference values with R PRE value exceeding 0.9, ratio of performance to deviation (RPD) ranging from 2.2 to 3.3 and low standard error of prediction. The models developed for key quality parameters also achieved strong predictive ability (R PRE > 0.95 and RPD = 2.5–6). These findings confirm that portable FTIR spectroscopy, coupled with pattern recognition modeling can offer breweries an accessible tool for real-time quality control and flavor stability monitoring across diverse beer varieties.